I. Field of the Invention
The present invention relates to wireless communications. More particularly, the present invention relates to a novel and improved searcher for detecting page messages in spread spectrum communications.
II. Description of the Related Art
In U.S. patent application Ser. No. 08/316,177 entitled xe2x80x9cMultipath Search Processor For A Spread Spectrum Multiple Access Communication Systemxe2x80x9d (The ""177 application) a searching for detecting spread spectrum signals is described. The searcher is particularly suited for use in a CDMA based digital cellular telephone system to identify pilot channels transmitted within the CDMA system. Once the pilot channel is identified, the telephone, or xe2x80x9csubscriber unit,xe2x80x9d uses the associated timing information to perform functions such as monitoring for page messages and conducting communications.
The ""177 searcher typically works in combination with a set of finger elements and decoder placed on a single integrated circuit. Together, the components perform the processing necessary for CDMA communications and page monitoring. For example, to receive a CDMA signal the searcher does pilot channel searching at various offsets in time. Once a pilot channel is detected, the finger elements are activated to process an associated data channel, such as a paging channel or a traffic channel. To perform the searching and the signal processing, the searcher and finger elements receive samples generated in response to RF signals received by the subscriber unit. The samples are typically generated by an RF/IF unit within the mobile phone or subscriber unit.
In general, it is desirable to reduce the power consumption of a subscriber unit to reduce the battery size and weight. Additionally, it is desirable to increase the reliability with which page and other messages are received and processed by the subscriber unit. It is to this end, as well as other objectives, that the present invention is directed.
The present invention is a novel and improved method for performing paging. In one embodiment of the invention a searcher is used to detect spread spectrum signals. Samples of received RF signals are stored in a sample buffer. During standby mode, the samples are gathered during paging slots assigned to the mobile. A set of searches are performed on the samples, and if pilot signals are detected additional demodulation is performed to detect paging messages. The resulting set of demodulation data may be combined to increase detection. After a page message has been detected, additional demodulation resources may be activated to processes more complete page messages, or other information channels. In one embodiment of the invention, the searcher includes a demodulator to perform quick page detection without the use of finger elements to reduce idle mode power consumption.